The present invention is directed generally to an electronic circuit for converting one type of electrical signal to another type of electrical signal, and more specifically to such an electronic circuit which converts an alarm signal from an alarm clock to a suitable signal level for energizing a conventional radio.
The invention is particularly useful in conjunction with a radio and an alarm clock which respectively normally operate from a DC source, for example the 12-volt system of a conventional automotive vehicle. Similar DC current systems are found in many automotive vehicles, recreational vehicles, campers, and boats. Hence, the present invention is equally useful in conjunction with any of the foregoing.
Conventional radios provided for operating from a DC source such as a 12volt automotive vehicle electrical system are well known. Additionally, DC operated alarm clocks are now available for use in automotive vehicles, and are similarly adapted to be operated from the vehicle 12-volt electrical system. However, these alarm clocks are presently provided with a buzzer or other similar audible alarm device and have no provision for energizing the vehicle radio to act as an alarm. These buzzers or other audible alarms generally require but a minimal signal voltage and current level for operation. Accordingly, the alarm clocks presently available provide such a low voltage, low current alarm signal output for energizing such a buzzer or other audible device. Consequently, the alarm signals produced by these digital alarm clocks are not suitable for energizing a conventional automotive vehicle radio.
Additionally, several types of alarm clocks are available which produce different types of alarms by producing output signals of different signal levels and polarities. For example, some digital alarm clocks provide an approximately 12-volt constant DC, low current signal to the alarm buzzer for a predetermined period upon reaching a preselected time, thereby sounding the buzzer continuously for some predetermined interval. Other digital alarm clocks and associated buzzers operate on a negative polarity signal. Still other alarm clocks produce a fixed DC level, pulsing signal to provide a pulsing buzzer or alarm sound. Moreover, these pulsing type of alarms may be at any of a plurality of different rates.
It will be appreciated from the foregoing that an alarm converter for energizing a radio for constant play at least over some predetermined period in response to an alarm signal from any of the foregoing types of alarm clocks is difficult to provide. Since none of the alarm clocks heretofore in use produce an alarm output signal suitable for directly driving a typical automotive vehicle radio, however, such a converter device must be utilized to obtain "radio" alarm.